Devices employing liquid crystals (LCs) have found use in a variety of electrooptical applications, in particular those which require compact, energy-efficient, voltage-controlled light valves, e.g., watch and calculator displays, as well as the flat-panel displays found in portable computers and compact televisions. Liquid crystal displays have a number of unique characteristics, including low voltage and low power of operation, which make them good candidates for use in non-emissive electrooptical display applications.
Polymer dispersed liquid crystal (PDLC) and polymer stabilized liquid crystal (PSLC) technologies have received much attention because of their potential utility for display applications. The polymerization of a cholesteric liquid crystal (ChLC)/monomer mixture at a temperature at which the ChLC and monomer are soluble but the resulting ChLC/polymer mixture is insoluble is described as polymerization induced phase separation (PIPS). The ChLC/monomer mixture is applied between two substrates, each having a conductive inner surface coating of a transparent conductor such as indium tin oxide (ITO). The monomer is then cured to give the ChLC cell. Application of an electric field (E) across the cell causes the ChLC to be aligned in either the planer (reflective) state phase or the focal conic (light scattering) phase. Both of these states are stable at E=0 which means that the textures are “locked in” and remain intact until acted upon again (i.e. the device is bistable). The reflected wavelength (λ) is controlled by formulating the ChLC with a chiral dopant of specific helical twisting power (HTP) at a concentration (c) where the helical pitch (Po) is given byPo=[(c)(HTP)]−1 
ChLC display technology may be useful in indoor applications such as retail point-of-purchase displays as well as for large format outdoor signage. However, outdoor applications require display panels with consistent color rendition over prolonged exposure to the environment. Thus, for ChLC display technology to be useful in outdoor applications, materials must be color stable under a wide variety of conditions, i.e., there should be no change in Po with time.